Peculiarities of secondary hardening of cemented steels

The causes leading to a high hardness of a case-hardened layer in the secondary hardening, and the influence of the content of austenite in a hardened state on this feature are studied. A greater secondary hardness of the case-hardened layer of the steels under studies, resulting from their tempering from the austenite state, can be explained by a formation of more disperse carbide particles due to less diffusion mobility of elements in austenite against the α-phase at the first cycles of tempering, and by lesser degree of the matrix phase mechanical hardening at the successive cycles of tempering, and also by difference in composition, and, consequently, in stability to coagulation of carbide particles separating from austenite and martensite